Axiomatizing Geometric Constructions
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Diameter, Width and Thickness in the Hyperbolic Plane
DIAMETER, WIDTH AND THICKNESS IN THE HYPERBOLIC PLANE AKOS´ G.HORVATH´ Abstract. This paper contains a new concept to measure the width and thickness of a convex body in the hyperbolic plane. We compare the known concepts with the new one and prove some results on bodies of constant width, constant diameter and given thickness. 1. Introduction In hyperbolic geometry there are several concepts to measure the breadth of a convex set. In the first section of this paper we introduce a new idea and compare it with four known ones. Correspondingly, we define three classes of bodies, bodies of constant with, bodies of constant diameter and bodies having the constant shadow property, respectively. In Euclidean space more or less these classes are agree but in the hyperbolic plane we need to differentiate them. Among others we find convex compact bodies of constant width which size essential in the fulfilment of this property (see Statement 7) and others where the size dependence is non-essential (see Statementst:circle). We prove that the property of constant diameter follows to the fulfilment of constant shadow property (see Theorem 2), and both of them are stronger as the property of constant width (see Theorem 1). In the last part of this paper, we introduce the thickness of a constant body and prove a variant of Blaschke’s theorem on the larger circle inscribed to a plane-convex body of given thickness. 1.1. The hyperbolic concepts of width (breadth) introduced earlier. 1.1.1. width ( ): Santal´oin his paper [14] developed the following approach. -
On the Standard Lengths of Angle Bisectors and the Angle Bisector Theorem
Global Journal of Advanced Research on Classical and Modern Geometries ISSN: 2284-5569, pp.15-27 ON THE STANDARD LENGTHS OF ANGLE BISECTORS AND THE ANGLE BISECTOR THEOREM G.W INDIKA SHAMEERA AMARASINGHE ABSTRACT. In this paper the author unveils several alternative proofs for the standard lengths of Angle Bisectors and Angle Bisector Theorem in any triangle, along with some new useful derivatives of them. 2010 Mathematical Subject Classification: 97G40 Keywords and phrases: Angle Bisector theorem, Parallel lines, Pythagoras Theorem, Similar triangles. 1. INTRODUCTION In this paper the author introduces alternative proofs for the standard length of An- gle Bisectors and the Angle Bisector Theorem in classical Euclidean Plane Geometry, on a concise elementary format while promoting the significance of them by acquainting some prominent generalized side length ratios within any two distinct triangles existed with some certain correlations of their corresponding angles, as new lemmas. Within this paper 8 new alternative proofs are exposed by the author on the angle bisection, 3 new proofs each for the lengths of the Angle Bisectors by various perspectives with also 5 new proofs for the Angle Bisector Theorem. 1.1. The Standard Length of the Angle Bisector Date: 1 February 2012 . 15 G.W Indika Shameera Amarasinghe The length of the angle bisector of a standard triangle such as AD in figure 1.1 is AD2 = AB · AC − BD · DC, or AD2 = bc 1 − (a2/(b + c)2) according to the standard notation of a triangle as it was initially proved by an extension of the angle bisector up to the circumcircle of the triangle. -
Advanced Euclidean Geometry
Advanced Euclidean Geometry Paul Yiu Summer 2016 Department of Mathematics Florida Atlantic University July 18, 2016 Summer 2016 Contents 1 Some Basic Theorems 101 1.1 The Pythagorean Theorem . ............................ 101 1.2 Constructions of geometric mean . ........................ 104 1.3 The golden ratio . .......................... 106 1.3.1 The regular pentagon . ............................ 106 1.4 Basic construction principles ............................ 108 1.4.1 Perpendicular bisector locus . ....................... 108 1.4.2 Angle bisector locus . ............................ 109 1.4.3 Tangency of circles . ......................... 110 1.4.4 Construction of tangents of a circle . ............... 110 1.5 The intersecting chords theorem ........................... 112 1.6 Ptolemy’s theorem . ................................. 114 2 The laws of sines and cosines 115 2.1 The law of sines . ................................ 115 2.2 The orthocenter ................................... 116 2.3 The law of cosines .................................. 117 2.4 The centroid ..................................... 120 2.5 The angle bisector theorem . ............................ 121 2.5.1 The lengths of the bisectors . ........................ 121 2.6 The circle of Apollonius . ............................ 123 3 The tritangent circles 125 3.1 The incircle ..................................... 125 3.2 Euler’s formula . ................................ 128 3.3 Steiner’s porism ................................... 129 3.4 The excircles .................................... -
4 3 E B a C F 2
See-Saw Geometry and the Method of Mass-Points1 Bobby Hanson February 27, 2008 Give me a place to stand on, and I can move the Earth. — Archimedes. 1. Motivating Problems Today we are going to explore a kind of geometry similar to regular Euclidean Geometry, involving points and lines and triangles, etc. The main difference that we will see is that we are going to give mass to the points in our geometry. We will call such a geometry, See-Saw Geometry (we’ll understand why, shortly). Before going into the details of See-Saw Geometry, let’s look at some problems that might be solved using this different geometry. Note that these problems are perfectly solvable using regular Euclidean Geometry, but we will find See-Saw Geometry to be very fast and effective. Problem 1. Below is the triangle △ABC. Side BC is divided by D in a ratio of 5 : 2, and AB is divided by E in a ration of 3 : 4. Find the ratios in which F divides the line segments AD and CE; i.e., find AF : F D and CF : F E. (Note: in Figure 1, below, only the ratios are shown; the actual lengths are unknown). B 3 E 5 4 F D 2 A C Figure 1 1My notes are shamelessly stolen from notes by Tom Rike, of the Berkeley Math Circle available at http://mathcircle.berkeley.edu/archivedocs/2007 2008/lectures/0708lecturespdf/MassPointsBMC07.pdf . 1 2 Problem 2. In Figure 2, below, D and E divide sides BC and AB, respectively, as before. -
AN INSTRUMENT in HYPERBOLIC GEOMETRY P. 290]
AN INSTRUMENT IN HYPERBOLIC GEOMETRY M. W. AL-DHAHIR1 In addition to straight edge and compasses, the classical instru- ments of Euclidean geometry, we have in hyperbolic geometry the horocompass and the hypercompass. By a straight edge, or ruler, we draw the line joining any two distinct points, and by the compasses we construct a circle with given center and radius. The horocompass is used to draw a horocycle through a given point when its diameter through the point with its direction are given. If the central line and radius of a hypercycle are given, we can draw it by the hypercompass. Although ruler and compasses have been generally used in the solutions of construction problems in hyperbolic geometry [l; 2, p. 191, pp. 204-206; 3, p. 394], other instruments have been intro- duced, and the relationships among these instruments, together with some restrictions, have been studied in recent years [2, pp. 289-291]. An important result in this connection is the following theorem [2, p. 290]. Theorem A. In conjunction with a ruler, the three compasses are equivalent. Recently [3, p. 389], a different geometrical tool, called the parallel-ruler, has been considered. For any point 4 and any ray a, not incident to 4, we can draw, with this ruler, a line through 4 parallel to a. As in Euclidean geometry, the parallel-ruler may also be used as an ordinary ruler. Hence the following result has been obtained [3]. Theorem H. Any construction that can be performed by a ruler and compasses can be performed by a parallel-ruler. -
Icons of Mathematics an EXPLORATION of TWENTY KEY IMAGES Claudi Alsina and Roger B
AMS / MAA DOLCIANI MATHEMATICAL EXPOSITIONS VOL 45 Icons of Mathematics AN EXPLORATION OF TWENTY KEY IMAGES Claudi Alsina and Roger B. Nelsen i i “MABK018-FM” — 2011/5/16 — 19:53 — page i — #1 i i 10.1090/dol/045 Icons of Mathematics An Exploration of Twenty Key Images i i i i i i “MABK018-FM” — 2011/5/16 — 19:53 — page ii — #2 i i c 2011 by The Mathematical Association of America (Incorporated) Library of Congress Catalog Card Number 2011923441 Print ISBN 978-0-88385-352-8 Electronic ISBN 978-0-88385-986-5 Printed in the United States of America Current Printing (last digit): 10987654321 i i i i i i “MABK018-FM” — 2011/5/16 — 19:53 — page iii — #3 i i The Dolciani Mathematical Expositions NUMBER FORTY-FIVE Icons of Mathematics An Exploration of Twenty Key Images Claudi Alsina Universitat Politecnica` de Catalunya Roger B. Nelsen Lewis & Clark College Published and Distributed by The Mathematical Association of America i i i i i i “MABK018-FM” — 2011/5/16 — 19:53 — page iv — #4 i i DOLCIANI MATHEMATICAL EXPOSITIONS Committee on Books Frank Farris, Chair Dolciani Mathematical Expositions Editorial Board Underwood Dudley, Editor Jeremy S. Case Rosalie A. Dance Tevian Dray Thomas M. Halverson Patricia B. Humphrey Michael J. McAsey Michael J. Mossinghoff Jonathan Rogness Thomas Q. Sibley i i i i i i “MABK018-FM” — 2011/5/16 — 19:53 — page v — #5 i i The DOLCIANI MATHEMATICAL EXPOSITIONS series of the Mathematical As- sociation of America was established through a generous gift to the Association from Mary P. -
Lectures – Math 128 – Geometry – Spring 2002
Lectures { Math 128 { Geometry { Spring 2002 Day 1 ∼∼∼ ∼∼∼ Introduction 1. Introduce Self 2. Prerequisites { stated prereq is math 52, but might be difficult without math 40 Syllabus Go over syllabus Overview of class Recent flurry of mathematical work trying to discover shape of space • Challenge assumption space is flat, infinite • space picture with Einstein quote • will discuss possible shapes for 2D and 3D spaces • this is topology, but will learn there is intrinsic link between top and geometry • to discover poss shapes, need to talk about poss geometries • Geometry = set + group of transformations • We will discuss geometries, symmetry groups • Quotient or identification geometries give different manifolds / orbifolds • At end, we'll come back to discussing theories for shape of universe • How would you try to discover shape of space you're living in? 2 Dimensional Spaces { A Square 1. give face, 3D person can do surgery 2. red thread, possible shapes, veered? 3. blue thread, never crossed, possible shapes? 4. what about NE direction? 1 List of possibilities: classification (closed) 1. list them 2. coffee cup vs donut How to tell from inside { view inside small torus 1. old bi-plane game, now spaceship 2. view in each direction (from flat torus point of view) 3. tiling pictures 4. fundamental domain { quotient geometry 5. length spectra can tell spaces apart 6. finite area 7. which one is really you? 8. glueing, animation of folding torus 9. representation, with arrows 10. discuss transformations 11. torus tic-tac-toe, chess on Friday Different geometries (can shorten or lengthen this part) 1. describe each of 3 geometries 2. -
Foundations of Euclidean Constructive Geometry
FOUNDATIONS OF EUCLIDEAN CONSTRUCTIVE GEOMETRY MICHAEL BEESON Abstract. Euclidean geometry, as presented by Euclid, consists of straightedge-and- compass constructions and rigorous reasoning about the results of those constructions. A consideration of the relation of the Euclidean “constructions” to “constructive mathe- matics” leads to the development of a first-order theory ECG of “Euclidean Constructive Geometry”, which can serve as an axiomatization of Euclid rather close in spirit to the Elements of Euclid. Using Gentzen’s cut-elimination theorem, we show that when ECG proves an existential theorem, then the things proved to exist can be constructed by Eu- clidean ruler-and-compass constructions. In the second part of the paper we take up the formal relationships between three versions of Euclid’s parallel postulate: Euclid’s own formulation in his Postulate 5, Playfair’s 1795 version, which is the one usually used in modern axiomatizations, and the version used in ECG. We completely settle the questions about which versions imply which others using only constructive logic: ECG’s version im- plies Euclid 5, which implies Playfair, and none of the reverse implications are provable. The proofs use Kripke models based on carefully constructed rings of real-valued functions. “Points” in these models are real-valued functions. We also characterize these theories in terms of different constructive versions of the axioms for Euclidean fields.1 Contents 1. Introduction 5 1.1. Euclid 5 1.2. The collapsible vs. the rigid compass 7 1.3. Postulates vs. axioms in Euclid 9 1.4. The parallel postulate 9 1.5. Polygons in Euclid 10 2. -
The Postulates of Neutral Geometry Axiom 1 (The Set Postulate). Every
1 The Postulates of Neutral Geometry Axiom 1 (The Set Postulate). Every line is a set of points, and the collection of all points forms a set P called the plane. Axiom 2 (The Existence Postulate). There exist at least two distinct points. Axiom 3 (The Incidence Postulate). For every pair of distinct points P and Q, there exists exactly one line ` such that both P and Q lie on `. Axiom 4 (The Distance Postulate). For every pair of points P and Q, the distance from P to Q, denoted by P Q, is a nonnegative real number determined uniquely by P and Q. Axiom 5 (The Ruler Postulate). For every line `, there is a bijective function f : ` R with the property that for any two points P, Q `, we have → ∈ P Q = f(Q) f(P ) . | − | Any function with these properties is called a coordinate function for `. Axiom 6 (The Plane Separation Postulate). If ` is a line, the sides of ` are two disjoint, nonempty sets of points whose union is the set of all points not on `. If P and Q are distinct points not on `, then both of the following equivalent conditions are satisfied: (i) P and Q are on the same side of ` if and only if P Q ` = ∅. ∩ (ii) P and Q are on opposite sides of ` if and only if P Q ` = ∅. ∩ 6 Axiom 7 (The Angle Measure Postulate). For every angle ∠ABC, the measure of ∠ABC, denoted by µ∠ABC, isa real number strictly between 0 and 180, determined uniquely by ∠ABC. Axiom 8 (The Protractor Postulate). -
The Steiner-Lehmus Theorem an Honors Thesis
The Steiner-Lehmus Theorem An Honors ThesIs (ID 499) by BrIan J. Cline Dr. Hubert J. LudwIg Ball State UniverSity Muncie, Indiana July 1989 August 19, 1989 r! A The Steiner-Lehmus Theorem ; '(!;.~ ,", by . \:-- ; Brian J. Cline ProposItion: Any triangle having two equal internal angle bisectors (each measured from a vertex to the opposite sIde) is isosceles. (Steiner-Lehmus Theorem) ·That's easy for· you to say!- These beIng the possible words of a suspicIous mathematicIan after listenIng to some assumIng person state the Steiner-Lehmus Theorem. To be sure, the Steiner-Lehmus Theorem Is ·sImply stated, but notoriously difficult to prove."[ll Its converse, the bIsectors of the base angles of an Isosceles trIangle are equal, Is dated back to the tIme of EuclId and is easy to prove. The Steiner-Lehmus Theorem appears as if a proof would be simple, but it is defInItely not.[2l The proposition was sent by C. L. Lehmus to the Swiss-German geometry genIus Jacob SteIner in 1840 with a request for a pure geometrIcal proof. The proof that Steiner gave was fairly complex. Consequently, many inspIred people began searchIng for easier methods. Papers on the Steiner-Lehmus Theorem were prInted in various Journals in 1842, 1844, 1848, almost every year from 1854 untIl 1864, and as a frequent occurence during the next hundred years.[Sl In terms of fame, Lehmus dId not receive nearly as much as SteIner. In fact, the only tIme the name Lehmus Is mentIoned In the lIterature Is when the title of the theorem is gIven. HIs name would have been completely forgotten if he had not sent the theorem to Steiner. -
The Calculus: a Genetic Approach / Otto Toeplitz ; with a New Foreword by David M
THE CALCULUS THE CALCULUS A Genetic Approach OTTO TOEPLITZ New Foreword by David Bressoud Published in Association with the Mathematical Association of America The University of Chicago Press Chicago · London The present book is a translation, edited after the author's death by Gottfried Kothe and translated into English by LuiseLange. The German edition, DieEntwicklungder Infinitesimalrechnung,was published by Springer-Verlag. The University of Chicago Press,Chicago 60637 The University of Chicago Press,ltd., London © 1963 by The University of Chicago Foreword © 2007 by The University of Chicago All rights reserved. Published 2007 Printed in the United States of America 16 15 14 13 12 11 10 09 08 07 2 3 4 5 ISBN-13: 978-0-226-80668-6 (paper) ISBN-10: 0-226-80668-5 (paper) Library of Congress Cataloging-in-Publication Data Toeplitz, Otto, 1881-1940. [Entwicklung der Infinitesimalrechnung. English] The calculus: a genetic approach / Otto Toeplitz ; with a new foreword by David M. Bressoud. p. cm. Includes bibliographical references and index. ISBN-13: 978-0-226-80668-6 (pbk. : alk. paper) ISBN-10: 0-226-80668-5 (pbk. : alk. paper) 1. Calculus. 2. Processes, Infinite. I. Title. QA303.T64152007 515-dc22 2006034201 § The paper used in this publication meets the minimum requirements of the American National Standard for Information Sciences-Permanence of Paper for Printed Library Materials, ANSI Z39.48-1992. FOREWORDTO THECALCULUS: A GENETICAPPROACHBYOTTO TOEPLITZ September 30, 2006 Otto Toeplitz is best known for his contributions to mathematics, but he was also an avid student of its history. He understood how useful this history could be in in forming and shaping the pedagogy of mathematics. -
Euclidean Geometry
An Interactive Java Program to Generate Hyperbolic Repeating Patterns Based on Regular Tessellations Including Hyperbolic Lines and Equidistant Curves A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Sakethram Karumuri IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE Dr. Douglas Dunham July, 2015 © Sakethram Karumuri 2015 ALL RIGHTS RESERVED Acknowledgements I would like to gratefully acknowledge my advisor, Dr. Douglas Dunham whose constant guidance and support helped me in completing this thesis. Without his persistent help, this work would not have been completed. I would like to thank my committee members, Dr. Peter Willemsen and Dr. Steven Trogdon for their support and encouragement. I would like to thank my exceptional department faculty, especially Dr. Ted Pedersen, Dr. Huayang Wang and Dr. Hudson Turner for teaching me the nitty gritty of Computer Science concepts. I would like to thank Lori Lucia and Clare Ford for providing support in times of need. I would also like to thank all my friends and fellow graduate students especially Shiva Kumar Chittamuru and Mounika Alla for sharing their knowledge and experience which helped me to complete my thesis. Finally, I would like to thank my parents and my sister for their unconditional trust and timely encouragement. It was their love that helped me rise up during the times of adversity. i Dedicated to my mom, Mrs. Savitri Karumuri, my dad, Mr. Syam Babu Karumuri, and my sister, Mrs. Prathyusha Gunishetty ii Abstract Repeating patterns have been utilized as art by various cultures all through the history.